I would like the div, fieldset and panel widths to stay intact. When the columns in the grid increase, a horizontal scrollbar should appear for the panel. I am unable to figure that out. The panel & grid are going out of the fieldset.

Articles are so generic and always not helpful. Please see if you can provide a solution. If you have checked the fiddle, I already used overflow. Its just that , they are not working as expected and should be done another way.